A pressure-sensitive adhesive tape or sheet comprising a polyvinyl chloride based film as a base material (hereinafter sometimes referred to as “polyvinyl chloride pressure-sensitive adhesive tape”) has been used in, for example, wire binding or electric insulation in household appliances or automobiles, or masking application at the time of painting. However, in recent years, from the viewpoint of an environmental issue, a trend of inhibiting the use of vinyl chloride is expanding in various fields, and as to the use of polyvinyl chloride pressure-sensitive adhesive tapes, the same tendency is observed.
In such a trend, various investigations have been made with respect to pressure-sensitive adhesive tapes free from polyvinyl chloride as a base material component. However, it is the present state that in the case of comparison with conventional polyvinyl chloride pressure-sensitive adhesive tapes, pressure-sensitive adhesive tapes having sufficient superiority are not developed yet from the viewpoints of performance and productivity.
On the other hand, as a substitute for polyvinyl chloride, various polyolefin based resins such as polyethylene, polypropylene, and olefin based elastomers are often used (see Patent Documents 1 to 4). Incidentally, these polyolefin based resins are formed into a film or sheet by extrusion molding or calender molding.
[Patent Document 1]
JP-A-2001-192629
[Patent Document 2]
JP-A-5-194915
[Patent Document 3]
JP-A-5-47249
[Patent Document 4]
JP-A-2001-311061
(The term “JP-A” as used herein means an “unexamined published Japanese patent application”)
Hitherto, the production of a polyvinyl chloride film or sheet as a base material of polyvinyl chloride pressure-sensitive adhesive tape was carried out by the rolling system using calender rolls. In this case, in calender rolling, a system in which four calender rolls arranged in the reverse L shape are driven by one motor (single drive system) was generally employed. However, in the case of forming a resin composition containing a polyolefin based resin as the major component (polyolefin based resin composition) into a film by the single drive system that has hitherto been employed for the production of a polyvinyl chloride film or sheet, excessive loading of a motor occurs between the respective rolls (calender rolls), it is difficult to perform rolling at a high speed, and hence, it is difficult to design an enhancement of the productivity. Also, a scattering in characteristics or physical properties of the resulting base material for pressure-sensitive adhesive tape or sheet (or pressure-sensitive adhesive tape or sheet) is large. For example, if a scattering in characteristic regarding stress-strain is large, tearability of the pressure-sensitive adhesive tape lowers, or cutting in winding the pressure-sensitive adhesive tape becomes difficult, resulting in a lowering of the winding workability.